Ocular insert

ABSTRACT

Drug-dispensing ocular insert is comprised of a flexible body of polymeric material that is insoluble in tear liquid and has an imperforate surface. The polymeric material contains a drug which is dispensed to the eye in a therapeutically effective amount by diffusion through the polymeric material. The ocular insert is adapted for insertion in the cul-de-sac of the conjunctiva between the sclera of the eyeball and the lower lid, to be held in place against the eyeball by the pressure of the lid.

United States Patent Inventor Richard A. Ness Fergus Falls, Minn. App].No. 831,761 Filed June 9, 1969 Patented Nov. 9, 1971 Assignee AlzaCorporation OCULAR INSERT 21 Claims, 2 Drawing Figs. US. Cl. 128/260,128/156 lnt .Cl ..A6lm 31/00 Field 01 Search 128/260, 296, 156

[56] References Cited UNITED STATES PATENTS 3,220,960 1 1/ 1965Wichterle 260/25 3,339,546 9/1967, Chen 128/156 3,416,530 12/1968 Ness128/260 Primary Examiner-Robert W. Michell Assistant ExaminerR. P. DyerAttorney-Steven D. Goldby ABSTRACT: Drug-dispensing ocular insert iscomprised of a flexible body of polymeric material that is insoluble intear liquid and has an imperforate surface. The polymeric materialcontains a drug which is dispensed to the eye in a therapeuti callyeffective amount by diffusion through the polymeric material. The ocularinsert is adapted for insertion in the culde-sac of the conjunctivabetween the sclera of the eyeball and the lower lid, to be held in placeagainst the eyeball by the pressure of the lid.

PATENTEUNUV 91971 3.618504 mvsmron RICHARD A. NESS BACKGROUND OF THEINVENTION This invention relates to an ocular insert for dispensingdrugs to the eye over a prolonged period of time.

At the present time, diseases of the eye are treated by applyingophtahalmic drugs in liquid or ointment form. To be effective in manycases, the application of drug should be substantially continuous. Suchcontinuous delivery of drug is not obtained through the use of liquid orointment dosage forms, even though they be applied at intervals duringthe day and night. Periodic application of these dosage forms results inthe eye receiving a massive, but unpredictable, amount of drug at thetime of application but the drug is washed away rapidly by tears,leaving the eye without medication until the nextapplication. Ointmentdosage forms are presently available only in unsterilized form and thistoo presents a problem.

At a very early time, drugs were dissolved or'dispersed in awater-soluble gel of gylcerinated gelatin that was shaped to the form ofa lamella or eye disk. These lamellae were applied to the inner surfaceof the eyelid to supply drug to the eye. In use, the glycerinatedgelatin vehicle liquid, producing the fonns. Lamellae were same type ofeffect as liquid dosage not a sustained-release dosage form. To myknowledge, they are not used in this country, although they may be' usedto a small extent in Europe. Further information on these water-solubledosage forms can be found in Remingtons Pharmaceutical Sciences, Xlll,pages 547-8 (Mack Publishing Co., Easton, Pa. 1965); Fishbum, AnIntroduction to Pharmaceutical Formulation, page 116 (Pergamon PressLtd, New York Cit NY. 1965); and U.S. Pat. No. 273,410,Mar.6, 1883.

U.S. Pat. No. 3,416,530, granted Dec. 17, 1968, and assigned to theassignee of this invention, is directed to my invention of adrug-dispensing ocular insert that truly acts as a depot or drugreservoir, retaining and slowly releasing drug to the eye for prolongedperiods of time. Such ocular inserts are fabricated of flexiblepolymeric materials that are biologically inert, nonallergenic, andinsoluble in tear liquid. To initiate the therapeutic program, theocular insert is placed in the culde-sac of the conjunctiva between thesclera of the eyeball and the lid. Since the polymeric material fromwhich the ocular insert is formed is insoluble in tear liquid it retainsits integrity and remains intact during the course of therapy, acting asa reservoir to continuously release drug to the eye and sur roundingtissues at a rate which is not affected by dissolution or erosion of thepolymeric material. On termination of the therapeutic program, theocular insert is removed from the cul-de-sac. Thus, a single such ocularinsert provides the complete ophthalmic dosage regime for a particulartime period, on the order of 24 hours or longer. Frequent repeatedapplications, as is necessary with liquids, ointments, or watersolublelamellae, often requiring awakening the patient during the night, areavoided.

To provide for release of ophthalmic drug from the polymeric body of theocular insert, U.S. Pat. No. 3,416,530 describes using polymericmaterials which are perforated with capillary openings. While thesecapillary openings are effective to release drug to the eye, they addconsiderable complexity to the manufacture of ocular inserts; for its isdifficult to control the size of these openings in large-scalemanufacturing using various polymers.

The best mode contemplated for practicing the invention of U.S. Pat.3,416,530, was, at the time the patent application maturing to thatpatent was filed, to place the ocular insert under the upper eyelid ingenerally radically spaced relation to the cornea of the eyeball and inthe path of flow of tears from the associated lachrymal gland. However,the eye has a tendency to roll upwardly during sleeping a process knownas Bell's Phenomenon, which may cause discomfort to some persons if theocular insert is under the upper lid.

dissolved'rapidly in tear 2 SUMMARY OF THE INVENTION dispensing ocularinsert which delivers drugs to the eye at a controlled rate, that is notnumber of perforations or ocular insert. 7

Still another object of this invention dependent upon the size and poresin the polymeric body of the is to provide a drugdispensing ocularinsert which is comfortable to wear for long resides in adrug-dispensing ocular insert periods and does not cause discomfortduring sleeping and normal daily wear. In accomplishing these objects,one feature of this invention to deliver during to the eye overaprolonged period of time, comprising a flexible ody of polymericmaterial insoluble in tear liquid and having an imperforate surface, thebody containing a drugwhichis dispensed to the eye in a therapeuticallyeffective amount by diffusion through the polymeric material. The ocularinsert of this invention is adapted for insertion in the cul-de-sac ofthe conjunctiva betweenthe sclera of the eyeball and the lower lid, tobe held in place against the eyeball by the pressure of the lid.

Other objects features and advantages of the invention will become moreapparent from the following description of the invention and from theclaims.

.Belgian Pat. No. 701,813),

DETAILED DESCRlPTlON or THE INVENTION In accordance with this invention,insert is designed for placement and eyelid and is fabricated of aperforate surface, that therethrough.

Polymeric materials used in forming the ocular insert are flexible,biologically inert, insoluble in tear liquid, and nonallergenic. It isimportant that thepolyrneric material be capable of transferring thedrug through its unbrokenwalls by the diffusion of drug or drug solutiontherethrough. By utilizing the mechanism of difiusion to dispense drugto the eye, the rate of drug release can be controlled with precisionand reproducibility. In each case, selection of the polymeric materialis dependent on the particular drug and drug form to be used in thedevice. Exemplary materials forfabricating the ocular insert includehydrophobic polymers such as plasticized or unplasticizedpolyvinylchloride, plasticized nylon, unplasticized soft nylon,plasticized polyethylene terephtahalate, and silicone rubber; andhydrophilic polymers such as the hydrophilic hydrogels of esters ofacrylic and methacrylic acid (as described in U.S. Pat. Nos. 2,976,576and 3,220,960 and modified collagen, cross-linked hydrophilic polyethergels (as described in U.S. Pat. No. 3,419,006), cross-linkedpolyvinylalcohol, and cross-linked partially hydrolyzedpolyvinylacetate. When plasticizers are used to impart flexibility tothe polymer, various plasticizers kriown to the art can be employed,such as long-chain fatty amides, higher alcohols, and dioctyl phthalate.

Those skilled in the art will appreciate that many of the hydrophilicpolymers suitable for use in this invention absorb forming a hydrogeltherewith. Tear liquid entering to form the swollen hydrogel moleculesdissolves the drug within the polymeric body, and the resulting drugsolution then diffuses outwardly from: the the hydrogel structure.Therefore, as used in this specification and the appended claims, theterm diffusion? refers to the movement of a drug through an imperforatepolymeric body, as well as to the movement of adrug solution through animperforate body. Use of the expression insoluble in tear liquidf torefer to suitable polymeric materials, means that the polymericmaterials do not dissolve and erode as a result of the action of tearliquid, but may absorb tear liquid, forming a swollen hydrogel.

a drug-dispensing ocular retention under the lower polymeric material,having an imwill release drug by diffusion Any of the drugs used totreat the eye and surrounding tissues can be incorporated in the ocularinsert of this invention. Also, it is practical to use the eye andsurrounding tissues as a point of entry for systemic drugs that entercirculation in the blood stream and produce a phannacologic response ata site remote from the point of application of the ocular insert. Thus,drugs which will pass through the eye or the tissue surrounding the eyeto the bloodstream, but which are not used in therapy of the eye itself,can be incorporated in the ocular insert.

Suitable drugs for use in therapy of the eye with the ocular insertinclude, without limitation: Anti-infectives: such as antibiotics,including tetracycline, chlortetracycleine, bacitracin, neomycin,polymyxin, gramicidin, oxytetracycline, chloramphenicol, anderythromycin; sulfonamides, including sulfacetamide, sulfamethizole, andsulfisoxazole; antivirals, including idoxuridine; and otheranti-infectives including nitrofurazone and sodium propionate;Antiallergenics such as antazoline, methapyrilene, chlorpheniramine,pyrilamine and prophenpyridamine; Anti-inflammatories such ashydrocortisone, hydrocortisone acetate, dexamethasone, dexamethasone2l-phosphate, fluocinolone, medrysone, prednisolone, prednisoloneZI-phosphate and prednisolone acetate; Decongestants such asphenylephrine, naphazoline, and tetrahydrazoline; Miotics andanticholinesterases such as pilocarpine, eserine salicylate, carbachol,diisopropyl flur'ophosphate, phospholine iodide, and demecarium bromide;Mydriatics such as atropine sulfate, cyclopentolate, homatropine,scopolamine, tropicamide, eucatropine, and hydroxyamphetamine andSypathomimetics such as epinephrine. Drugs can be in various forms, suchas uncharged molecules, components of molecular complexes, ornonirritating, pharmacologically acceptable salts, such ashydrochloride, hydrobromide, sulfate phosphate, nitrate, borate,acetate, maleate, tartrate, salicylate, etc. Furthermore, simplederivatives of the drugs (such as ethers, esters, amides, etc.,) whichhave desirable retention and release characteristics but which areeasily hydrolyzed by body pH, enzymes, etc. can be employed. The amountof drug incorporated in the ocular insert varies widely, depending onthe particular drug, the desired therapeutic effect, and the time spanfor which the ocular insert will be used. Since the ocular insert isintended to provide the complete dosage regime for eye therapy for but aparticular time span, such as 24 hours, there is no critical upper limiton the amount of drug incorporated in the device. For when the device isremoved and disposed of it makes little difference whether any drugremains in the device. The lower limit will depend on the activity ofthe drug and its capability of being released from the device. Thus itis not practical to define a range for the therapeutically effectiveamount of drug incorporated into the device. However, typically, from Imicrogram to l milligram of drug is incorporated in the ocular insert.

In each case, the polymeric material used to form the ocular insert ischosen for its compatibility with a particular drug and its capabilityof releasing that drug by diffusion at an appropriate rate over aprolonged period of time. Specific, but nonlimiting, examples ofcombinations of drugs and polymers for use in forming the ocular insertare: (l) chloramphenicol incorporated into polyethylene terephthalateplasticized with higher alcohols; (2) promethazine trichloroacetateincorporated into polyvinylchloride plasticized with dioctylphthalate;(3) chloramphenicol dispersed throughout polydimethylsiloxane rubber;(4) pilocarpine or pilocarpine perfluorobutyrate incorporated intopolyvinylchloride plasticized with dioctylsebecate; and (5)dexamethasone incorporated into nylon-plasticized with higher alcohols.

The ocular insert can be fabricated in any convenient shape forcomfortable retention in the cul-de-sac. It is important, however, thatthe device have no sharp, jagged, or rough edges which can irritate thesensitive tissues of the eye. Thus the marginal outline of the ocularinsert can be ellipsoid, beanshaped, rectangular, etc. In cross section,in can be concavoconvex, rectangular, etc. As the ocular insert isflexible and, in used, will assume essentially the configuration of thescleral curvature, the original shape of the device is not ofcontrolling importance. Dimensions of the device can vary widely. Thelower limit on the size of the device is governed by the amount of theparticular drug to be applied to the eye and surrounding tissues toelicit the desired pharmacologic response, as well as by the smallestsized device which conveniently can be inserted and removed from theeye. The upper limit on the size of the device is governed by thelimited space within the culde-sac that conveniently and comfortably canbe filled with an ocular insert. Typically, the ocular insert is 4 to 20millimeters in length, l to 12 millimeters in width, and 0.1 to lmillimeter in thickness. Preferably it is ellipsoidal in shape and about6 X4 0.5 millimeters in size.

The ocular insert can be a polymeric matrix with the drug dispersedtherethrough or can be a sealed container with walls of polymericmaterial and having the drug in an interior chamber thereof. One suchcontainer has a circular or ellipsoidal cross section and is tapered atthe ends. Drug can be incorporated in the ocular insert in many ways.When the ocular insert is in the form of a container, any of theencapsulation, bonding, and coating techniques conventionally used inthe art can be employed. When the ocular insert is a solid matrix withthe drug dispersed therethrough, it can be fabricated by adding thedrugs to the monomers prior to polymerization; adding the drug to thepolymer in liquid form, molding and curing; or by impregnating thepolymeric material, either before or after shaping to the form of theocular insert, with the drug.

Referring particularly to FIG. 1 and 2, to use the ocular insert 10(shown by dot and dash lines in FIG. 1), it is placed in the cul-de-sacll of the conjunctiva 12 between sclera 13 of the eyeball l4 and thelower lid 15. The pressure of the lower lid 15 maintains the ocularinsert 10 in place. With the ocular insert 10 under the lower lid 15,the device is comfortable to the wearer and does not contact the cornea16 during sleeping nor during normal ocular motion. Once in place, theocular insert 10 functions as a drug reservoir gradually releasing drugto the eye and surrounding tissue. Drug 17 leaving the ocular insert bydiffusion is transported to the eyeball 14 by the flow of tear liquidand by the blinking action of the eyelids. By use of the ocular insert,the eye is continuously bathed with drug 17 over a particular time span.Normally, the ocular insert 10 will be retained in place for a period of24 hours, thereby supplying the complete dosage regime for eye therapyover that period of time. During the course of use, the polymeric body18 of the ocular insert does not dissolve or erode in tear liquid and apredictable and reproducible dosage regime is provided.

In a specific example of the manufacture of an ocular insert theinvention, liquid polydimethylsiloxane (dow Corning Silastic 382) ismixed with chloramphenicol antibiotic. After uniformly mixing theantibiotic with the unvulcanized silicone rubber, stannous octoatecatalyst (0.5 percent by weight) is added to the mixture is poured intoa mold having an ellipsoidal cavity 6 millimeters by 4 millimeters by0.5 millimeter to cure the silicone rubber at room temperature. Theresulting ocular insert formed of silicone rubber contains 0.5 milligramof chloramphenicol. When inserted in the cul-de-sac of the conjunctivabetween the sclera of the eyeball and the lower lid, the ocular insertis effective to deliver to the eye the dose of chloramphenicolantibiotic required for 24 hours of treatment of infection. After thatperiod of time, the ocular insert, with its dimensions unchanged, isremoved from the cul-desac and an identical insert placed in its steadto continue the therapeutic program for an additional 24 -hour period.

Thus, the improved ocular insert of this invention offers manyadvantages. As it is formed of a polymeric material, insoluble in tearliquid, the ocular insert does not dissolve or erode in tear liquidduring the course of therapeutic program. This permits the therapeuticprogram to be precisely controlled and the release of drug predictedwith accuracy. That the ocular insert releases drug by diffusion is mostimportant, since this too provides for close control over the rate ofdrug release from the polymer.

While there have been described and pointed out the fundamental novelfeatures of the invention as applied to the preferred embodiment, thoseskilled in the art will appreciate that various modifications, changes,and omissions in the ocular insert illustrated and described can be madewithout departing from the spirit of the invention. It is the intention,therefore, to be limited only by the scope of the following claims.

What is claimed is:

l. A medication-dispensing tablet for a human eyeball, said tabletcomprising a reservoir of drug formulation confined within a flexible,imperforate and continuous-surfaced body of nonallergenic polymericmaterial which is insoluble in tear liquid, said body being formed of adrug-release rate-controlling polymer to continuously meter the flow ofdrug by diffusion from the reservoir to the eye at a controlled,predetermined and reproducible rate over a prolonged period of time,said body being adapted for insertion into the cul-de-sac of theconjunctiva between the sclera of the eyeball and eyelid, to be held inplace against the eyeball by the pressure of the lid, and said bodyhaving a marginal outline and cross section adapted to assumeessentially the configuration of the scleral curvature; said drug beingcapable of transport through the unbroken walls of said body bydiffusion and said body being so constructed and arranged that, whenapplied to the eyeball, to dispense said drug leaving said body bydiffusion is transported to the eyeball by the flow of tears and by theblinking action of the eyelids.

2. The medication-dispensing tablet as defined by claim 1, wherein thereservoir of drug formulation is comprised of a sealed container withwalls of said polymeric material and said drug is contained in aninterior chamber thereof.

3. The medication-dispensing tablet as defined by claim 2, wherein saidpolymeric material is selected from the group consisting of plasticizedor unplasticized polyvinyl chloride, plasticized nylon, unplasticizedsoft nylon, plasticized polyethylene terephthalate, silicone rubber,hydrophilic hydrogel of an ester of acrylic or methacrylic acid,modified collagen, cross-linked hydrophilic polyether gel, cross-linkedpolyvinyl alcohol, and cross-linked partially hydrolyzed polyvinylacetate.

4. The medication-dispensing tablet as defined by claim 3, wherein saidpolymeric material is silicone rubber.

5. The medication-dispensing tablet as defined by claim 3, wherein saidpolymeric material is a hydrophilic hydrogel of an ester of acrylic ormethacrylic acid.

6. The medication-dispensing tablet as defined by claim 1, wherein thereservoir of drug formulation is comprised of a matrix of thedrug-release ratecontrolling polymeric material, said matrix having thedrug distributed therethrough.

7. The medication-dispensing tablet as defined by claim 1,

wherein said polymeric material is selected from the group consisting ofplasticized unplasticized polyvinyl chloride, plasticized nylon,unplasticized soft nylon, plasticized polyethylene terephthalate,silicone rubber, hydrophilic hydrogel of an ester of acrylic ormethacrylic acid, modified collagen, cross-linked hydrophilic polyethergel, cross-linked polyvinyl acetate.

8. The medication-dispensing tablet as defined by claim 7, wherein saidpolymeric material is silicone rubber.

9. The medication-dispensing tablet as defined by claim 7, wherein saidpolymeric material is a hydrophilic hydrogel of an ester of acrylic ormethacrylic acid.

10. The medication-dispensing tablet as defined by claim 1, wherein saiddrug is an ophthalmic drug.

11. The medication-dispensing tablet as defined by claim 1, wherein saiddrug is a systemically active drug which will pass through the eye tothe bloodstream and produce a pharmacologic response at a site remotefrom the eye.

vl2. The medication-dispensing tablet as defined by claim 1, whereinsaid drug is a systemically active drug which will pass through thetissue surrounding the eye to the bloodstream and produce apharmacologic response at a site remote from the l3. Themedication-dispensing tablet as defined by claim 1, wherein from 1microgram to l milligram of drug is incorporated in said tablet.

14. The medication-dispensing tablet as defined by claim 1,

I wherein same is circular in cross section and tapered at its ends.

15. The medication-dispensing tablet as defined by claim 1, wherein sameis ellipsoidal in cross section and tapered at its ends.

16. The medication-dispensing tablet as defined by claim I, wherein sameranges from 4 to 20 millimeters in length, l to 12 millimeters in width,and 0.1 to l millimeter in thickness.

17. The medication-dispensing tablet as defined by claim 1, wherein thedrug is chloramphenicol and the polymeric material is polyethyleneterephthalate.

18. The medication-dispensing tablet as defined by claim 1, wherein thedrug is promethazine trichloroacetate and the polymeric material ispolyvinyl chloride.

19 The medication-dispensing tablet as defined by claim 1, wherein thedrug is ehloramphenicol and the polymeric material ispolydimethylsiloxane rubber.

20. The medication-dispening tablet as defined by claim 1, wherein thedrug is a member selected from the group consisting of pilocarpine andpilocarpine perfiuorbutyrate and the polymeric material is polyvinylchloride.

21. The medication-dispensing tablet as defined by claim 1, wherein thedrug is dexamethasone and the polymeric material is nylon-66.

K i t i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3 8, 0 Dated November 9, 1971 Inventor(s) Richard A. Ness It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 8, "ophtahalmic" should read ophthalmic-; line 20,"gylcerinated" should read -glycerinated-; line 64, "its" should readit--; line 70, "radically" should read -radially-. Column 2, line 16,"during" should read drug-; line 50, "terephtahalate" should readterephthalate.

Column 3, line 13, "chlortetracycleine" should read --chlortetracycline;line 31, "Sypathomimetics" should read Sympathomimetics-; line 35,following the word "sulfate" insert a comma; line 69,"nylon-plasticized" should read nylon-66 plasticized-; line 75, "in",second occurrence,

should read -it-. Column 4, line 2, "used" should read use-; line 31,"FIG." should read -FIGS.-; line 50, after "insert" add of-; line 51,"dow" should read Dow--; line 55, "to" should read and. Claim 1, line12, delete the hyphen between "continuous" and "surfaced". Claim 1, line27, insert thereto, drug-- between "drug" and "leaving".

Claim 7, line 2, insert or between "plasticized" and "unplasticized".Claim 7, line 7, after "polyvinyl delete "acetate." and insert alcohol,and cross-linked partially hydrolyzed polyvinyl acetate.--. Claim 20,line 47, "perfluorbutyrate" should read perfluorobutyrate.

In all the claims, each occurrence, delete the hyphen between"medication" and "dispensing".

Signed and sealed this 2nd day of May 1972.

EM F'O-1050 (10-69) (SEAL) Attest:

EDWARD M.FLE'I'CHER, JR. 5055111 Li-U'l'l'SUtiJ-LLK Attesting Officer Comissioner of Patents USCOMM-DC 6O376-F69 U S GOVERNMENT PRINHNG OFFICE1969 0-366-334

1. A medication-dispensing tablet for a human eyeball, said tabletcomprising a reservoir of drug formulation confined within a flexible,imperforate and continuous-surfaced body of nonallergenic polymericmaterial which is insoluble in tear liquid, said body being formed of adrug-release rate-controlling polymer to continuously meter the flow ofdrug by diffusion from the reservoir to the eye at a controlled,predetermined and reproducible rate over a prolonged period of time,said body being adapted for insertion into the cul-de-sac of theconjunctiva between the sclera of the eyeball and eyelid, to be held inplace against the eyeball by the pressure of the lid, and said bodyhaving a marginal outline and cross section adapted to assumeessentially the configuration of the scleral curvature; said drug beingcapable of transport through the unbroken walls of said body bydiffusion and said body being so constructed and arranged that, whenapplied to the eyeball, to dispense said drug thereto, drug leaving saidbody by diffusion is transported to the eyeball by the flow of tears andby the blinking action of the eyelids.
 2. The medication-dispensingtablet as defined by claim 1, wherein the reservoir of drug formulationis comprised of a sealed container with walls of said polymeric materialand said drug is contained in an interior chamber thereof.
 3. Themedication-dispensing tablet as defined by claim 2, wherein saidpolymeric material is selected from the group consisting of plasticizedor unplasticized polyvinyl chloride, plasticized nylon, unplasticizedsoft nylon, plasticized polyethylene terephthalate, silicone rubber,hydrophilic hydrogel of an ester of acrylic or methacrylic acid,modified collagen, cross-linked hydrophilic polyether gel, cross-linkedpolyvinyl alcohol, and cross-linked partially hydrolyzed polyvinylacetate.
 4. The medication-dispensing tablet as defined by claim 3,wherein said polymeric material is silicone rubber.
 5. Themedication-dispensing tablet as defined by claim 3, wherein saidpolymeric material is a hydrophilic hydrogel of an ester of acrylic ormethacrylic acid.
 6. The medication-dispensing tablet as defined byclaim 1, wherein the reservoir of drug formulation is comprised of amatrix of the drug-release rate-controlling polymeric material, saidmatrix having the drug distributed therethrough.
 7. Themedication-dispensing tablet as defined by claim 1, wherein saidpolymeric material is selected from the group consisting of plasticizedunplasticized polyvinyl chloride, plasticized nylon, unplasticized softnylon, plasticized polyethylene terephthalate, silicone rubber,hydrophilic hydrogel of an ester of acrylic or methacrylic acid,modified collagen, cross-linked hydrophilic polyether gel, cross-linkedpolyvinyl alcohol, and cross-linked partially hydrolyzed polyvinylacetate.
 8. The medication-dispensing tablet as defined by claim 7,wherein said polymeric material is silicone rubber.
 9. Themedication-dispensing tablet as defined by claim 7, wherein saidpolymeric material is a hydrophilic hydrogel of an ester of acrylic ormethacrylic acid.
 10. The medication-dispensing tablet as defined byclaim 1, wherein said drug is an ophthalmic drug.
 11. Themedication-dispensing tablet as defined by claim 1, wherein said drug isa systemically active drug which will pass through the eye to thebloodstream and produce a pharmacologic response at a site remote fromthe eye.
 12. The medication-dispensing tablet as defined by claim 1,wherein said drug is a systemically active drug which will pass throughthe tissue surrounding the eye to the bloodstream and produce apharmacologic response at a site remote from the eye.
 13. Themedication-dispensing tablet as defined by claim 1, wherein from 1microgram to 1 milligram of drug is incorporated in said tablet.
 14. Themedication-dispensing tablet as defined by claim 1, wherein same iscircular in cross section and tapered at its ends.
 15. Themedication-dispensing tablet as defined by claim 1, wherein same isellipsoidal in cross section and tapered at its ends.
 16. Themedication-dispensing tablet as defined by claim 1, wherein same rangesfrom 4 to 20 millimeters in length, 1 to 12 millimeters in width, and0.1 to 1 millimeter in thickness.
 17. The medication-dispensing tabletas defined by claim 1, wherein the drug is chloramphenicol and thepolymeric material is polyethylene terephthalate.
 18. Themedication-dispensing tablet as defined by claim 1, wherein the drug ispromethazine trichloroacetate and the polymeric material is polyvinylchloride. 19 The medication-dispensing tablet as defined by claim 1,wherein the drug is chloramphenicol and the polymeric material ispolydimethylsiloxane rubber.
 20. The medication-dispensing tablet asdefined by claim 1, wherein the drug is a member selected from the groupconsisting of pilocarpine and pilocarpine perfluorobutyrate and thepolymeric material is polyvinyl chloride.
 21. The medication-dispensingtablet as defined by claim 1, wherein the drug is dexamethasone and thepolymeric material is nylon-66.